1. Field of the Invention
The present invention relates to a method of manufacturing a ring spring for composite machinery seals and, more particularly, to an improved method of making an elastomeric resilient ring spring for use in an annular elastomeric boot of the U-cup type having an exposed annular groove which is generally x-shaped.
2. Description of the Prior Art
The use of composite machinery seals including a generally annular seal, frequently referred to as a boot or a U-cup, which has an exposed annular groove in one side thereof adapted to receive a resilient ring spring is well known. Commonly, such composite machinery seals are adapted for use with a ring spring which is a conventional O-ring. The primary advantage of a ring spring which is an O-ring is that it is simple and inexpensive to manufacture in a conventional mold.
In order to improve the performance of such a composite machinery seal, it has been proposed to modify the surface defining the annular groove in the U-cup and the shape of the elastomeric resilient ring spring so that both are generally x-shaped. A composite machinery seal with such a configuration is described in U.S. Pat. No. 3,851,888, issued Dec. 3, 1974 and reference should be had to such patent for a discussion of the advantages of such a configuration.
While a composite machinery seal of the configuration described in the before-mentioned U.S. Pat. No. 3,851,888 performs substantially better than a similar composite machinery seal using a conventional O-ring, substantial problems have limited its use. More specifically, the preferred method of manufacturing the ring spring is to mold same using a mold having a cavity which has a cross-sectional shape similar to the groove in the boot. However, it is expensive to manufacture a mold with a cavity of this shape and it is somewhat difficult to eject the ring from the mold after the molding operation. The result has been that it is significantly more expensive to mold a ring spring having a generally x-shape than a ring spring having a generally O-shape. In fact, the manufacturing cost is so much higher that it is competitively impractical to mold such a ring spring.
Therefore, the common approach today is to extrude the ring spring in a continuous length and to subsequently cut strips for use in the boots. While this is substantially less expensive, problems still remain. More specifically, labor costs are now high because the lengths must be individually measured and cut. Furthermore, once a ring spring is inserted into a boot, there is a break in the ring spring and it is common for the ring spring or a portion thereof to come out of the groove in the boot during assembly of the boot into a machine part. An economically practical solution to these problems has been unavailable heretofore.